More than 600,000 persons in the United States are morbidly obese with body weights twice the norm or 100 lbs above it. Excess morbidity and mortality occurs from coronary and cerebrovascular disease and diabetes. Because morbid obesity is resistant to dietary measures, gastric reduction by surgery is now a common treatment. The surgery has a mortality rate of about 2% and a morbidity rate of 6-9%. About half the operated patients fail to lose 15% of initial body weight. A less invasive procedure to reduce gastric capacity for food involves nonsurgical insertion of a balloon into the stomach. The effects of a detachable chronic silicone-rubber intragastric balloon on body weight and body fat, spontaneous food intake, gastric emptying rate, and serum glucose, insulin, glucagon, gastrin, and CCK-8 levels will be determined in morbidly obese subjects. Body fat will be estimated from antropometric indices and underwater weighing. Spontaneous intake of solid meals will be measured with a computerized eating monitor which records the weight of the food plate without the subject's knowledge. Spontaneous intake of liquid meals will be measured with an electronically monitored liquid dispensing device. When a button is pressed, the device delivers via a mouthpiece a precise predetermined volume of nutritionally complete liquid food. Gastric emptying rate will be determined with a computerized gamma camera after ingestion of liquid and solid meals containing Technetium 99-m. Repeated endoscopic examinations of the gastric mucosa will be made. A detachable intragastric balloon will be inserted and inflated to 400 ml (1:1 air:water) in two-thirds of the patients. Sixty patients divided into three groups will undergo for 1 year: (1) intragastric balloon; (2) intragastric balloon and a diet of 1000 kcal/day; and (3) diet alone. The patients will be followed up for 1 year to assess the persistence of the weight change. The proposed study will serve as a clinical trial of a new modality treatment for morbid obesity.